.TH std::acosh,std::acoshf,std::acoshl 3 "2024.06.10" "http://cppreference.com" "C++ Standard Libary"
.SH NAME
std::acosh,std::acoshf,std::acoshl \- std::acosh,std::acoshf,std::acoshl

.SH Synopsis
   Defined in header <cmath>
   float       acosh ( float num );

   double      acosh ( double num );                            (until C++23)

   long double acosh ( long double num );
   /* floating-point-type */                                    (since C++23)
               acosh ( /* floating-point-type */ num );         (constexpr since C++26)
   float       acoshf( float num );                     \fB(1)\fP \fB(2)\fP \fI(since C++11)\fP
                                                                (constexpr since C++26)
   long double acoshl( long double num );                   \fB(3)\fP \fI(since C++11)\fP
                                                                (constexpr since C++26)
   Additional overloads \fI(since C++11)\fP
   Defined in header <cmath>
   template< class Integer >                                (A) (constexpr since C++26)
   double      acosh ( Integer num );

   1-3) Computes the inverse hyperbolic cosine of num.
   The library provides overloads of std::acosh for all cv-unqualified floating-point
   types as the type of the parameter.
   (since C++23)

   A) Additional overloads are provided for all integer types, which are  \fI(since C++11)\fP
   treated as double.

.SH Parameters

   num - floating-point or integer value

.SH Return value

   If no errors occur, the inverse hyperbolic cosine of num (cosh-1
   (num), or arcosh(num)) on the interval [0, +∞], is returned.

   If a domain error occurs, an implementation-defined value is returned (NaN where
   supported).

.SH Error handling

   Errors are reported as specified in math_errhandling.

   If the argument is less than 1, a domain error occurs.

   If the implementation supports IEEE floating-point arithmetic (IEC 60559),

     * if the argument is less than 1, FE_INVALID is raised an NaN is returned.
     * if the argument is 1, +0 is returned.
     * if the argument is +∞, +∞ is returned.
     * if the argument is NaN, NaN is returned.

.SH Notes

   Although the C standard (to which C++ refers for this function) names this function
   "arc hyperbolic cosine", the inverse functions of the hyperbolic functions are the
   area functions. Their argument is the area of a hyperbolic sector, not an arc. The
   correct name is "inverse hyperbolic cosine" (used by POSIX) or "area hyperbolic
   cosine".

   The additional overloads are not required to be provided exactly as (A). They only
   need to be sufficient to ensure that for their argument num of integer type,
   std::acosh(num) has the same effect as std::acosh(static_cast<double>(num)).

.SH Examples


// Run this code

 #include <cerrno>
 #include <cfenv>
 #include <cfloat>
 #include <cmath>
 #include <cstring>
 #include <iostream>

 // #pragma STDC FENV_ACCESS ON

 int main()
 {
     std::cout << "acosh(1) = " << std::acosh(1) << '\\n'
               << "acosh(10) = " << std::acosh(10) << '\\n'
               << "acosh(DBL_MAX) = " << std::acosh(DBL_MAX) << '\\n'
               << "acosh(Inf) = " << std::acosh(INFINITY) << '\\n';

     // error handling
     errno = 0;
     std::feclearexcept(FE_ALL_EXCEPT);

     std::cout << "acosh(0.5) = " << std::acosh(0.5) << '\\n';

     if (errno == EDOM)
         std::cout << "    errno == EDOM: " << std::strerror(errno) << '\\n';
     if (std::fetestexcept(FE_INVALID))
         std::cout << "    FE_INVALID raised\\n";
 }

.SH Possible output:

 acosh\fB(1)\fP = 0
 acosh\fB(10)\fP = 2.99322
 acosh(DBL_MAX) = 710.476
 acosh(Inf) = inf
 acosh(0.5) = -nan
     errno == EDOM: Numerical argument out of domain
     FE_INVALID raised

.SH See also

   asinh
   asinhf              computes the inverse hyperbolic sine
   asinhl              (\\({\\small\\operatorname{arsinh}{x}}\\)arsinh(x))
   \fI(C++11)\fP             \fI(function)\fP
   \fI(C++11)\fP
   \fI(C++11)\fP
   atanh
   atanhf              computes the inverse hyperbolic tangent
   atanhl              (\\({\\small\\operatorname{artanh}{x}}\\)artanh(x))
   \fI(C++11)\fP             \fI(function)\fP
   \fI(C++11)\fP
   \fI(C++11)\fP
   cosh
   coshf               computes hyperbolic cosine (\\({\\small\\cosh{x}}\\)cosh(x))
   coshl               \fI(function)\fP
   \fI(C++11)\fP
   \fI(C++11)\fP
   acosh(std::complex) computes area hyperbolic cosine of a complex number
   \fI(C++11)\fP             (\\({\\small\\operatorname{arcosh}{z}}\\)arcosh(z))
                       \fI(function template)\fP
   C documentation for
   acosh

.SH External links

     Weisstein, Eric W. "Inverse Hyperbolic Cosine." From MathWorld — A Wolfram Web
     Resource.
